It is well known that the basic configuration for a switchable dual field of view objective system is that of a front lens and a rear lens spaced apart along a common optical axis with an intermediate lens switchable between an in-use position when the intermediate lens is located on-axis intercepting the ray envelope between the front and rear lenses, and an out-of-use position when the intermediate lens is located out of the ray envelope between the front and rear lenses. The intermediate lens itself is usually formed by separate lens elements.
It is an object of the present invention to provide a compact form of switchable dual field of view objective system with minimal number of lens elements so that it is light in weight and with a simple arrangement providing common field of view focusing for varying object distances at varying temperatures.